I'll be the contrarian: I don't think it's an important upgrade. There's nothing wrong with it, of course, but if you're dedicated to having fun and being a casual buoy chaser, then do that: have fun!
If you have any energy and money left, spend it on getting better. Get some coaching. Sounds like you already ski in different environments (wind, boats, etc.); this makes you a more robust skier. Worrying about PP vs ZBox vs ZO, or the minute differences between two boats makes you a more sensitive skier, more frustrated when one little element (boat, fin, wind, etc.) is just a tiny bit off.
BallOfSpray is a great place to come and get thinking about how to be a better skier. However, as a community of passionate ski nerds, it's also a place where you can come and see people arguing about very tiny things: the difference in wakes between one boat model year and the next, the difference between one setting on zero off and the next, the difference of a couple of thousandth of an inch in a fin setting. We have a tendency to make these differences sound like the difference between riding a child's tricycle vs a 1200cc sport bike, but they're not that big. For folks trying to improve their PB from 2 @ -39 to 3 @ -39, they're important discussions, for sure. But I wonder for many of us if the investment of energy and attention in these tiny factors provides a return in terms of happiness and satisfaction. I wonder if they make us more robust or more sensitive skiers. It sounds like you're having fun. -15/-22 @ 30/32mph is good skiing. You can't do it without getting a lot of things right. Sounds like you're having fun... keep having fun! You can do that behind PP classic, Stargazer, ZBox or ZO. Hey, we grew up doing it behind hand-driven outboards.